Wadi is the Arabic term traditionally referring to a valley; in some cases it may refer to a dry riverbed that contains water only during times of heavy rain or simply an intermittent stream.

when it does rain in deserts water is a powerful ersion force. it can carve out a river valley called a wadi during flash floods.

Because of constant freezing and thawing, the head of the glacier plucks out the side of the mountain and a circular amphitheater is cut into the peak. This huge, armchair-like depression with its vertical sides and basin-like floor is known as a cirque.